The present invention relates to a composition and method for reducing plant transpiration and, in particular, to a chitosan composition and method for applying the chitosan composition to plant foliage to reduce transpiration, to reduce drought-induced wilting, and to reduce water use by crops.
Drought poses a serious problem for agriculture. Water shortages can greatly adversely affect crop yield. While crop irrigation during periods of low rainfall and drought is a solution to decreased crop yield and plant death, significant expense is associated with irrigation. Thus, alternatives to irrigation including methods for maintaining healthy crops during drought periods are continuously sought.
The present invention relates to a chitosan composition and method for reducing transpiration and preventing drought-induced wilting in plants. In the method, a chitosan composition is applied to plant foliage in an amount and with a frequency sufficient to affect a reduction in transpiration and wilting.
Chitosan is a derivative of chitin, a polysaccharide consisting predominantly of unbranched chains of N-acetyl-D-glucosamine residues (i.e., xcex2-1,4-linked 2-acetamido-2-deoxy-D-glucose). Chitosan is produced by the deacetylation of chitin. Chitin can be regarded as a cellulose derivative in which the C-2 hydroxyl groups have been replaced by acetamido residues. Chitin is found in fungi, yeast, and abundantly in marine invertebrates and arthropods where it is a principal component of the exoskeleton. Chitin is commercially available from a number of sources and is typically prepared from crab shells. Chitin and chitosan are polysaccharides that differ in the extent of glucosamine acetylation. Pure 100% acetylated chitin does not occur naturally and chitosan is generally not 100% deacetylated. Rather, chitin polysaccharides consist of both acetylated and non-acetylated glucosamine residues within the polysaccharide chains. The percentage of acetylated D-glucosamine residues within chitin polysaccharide chains is higher compared to the non-acetylated D-glucosamine residues. Similarly, chitosan polysaccharides consist of both acetylated and non-acetylated D-glucosamine residues but contain a higher percentage of non-acetylated D-glucosamine residues relative to acetylated D-glucosamine residues.
Chitin has been used for a wide variety of purposes. For example, chitin has been used in wound healing compositions, as an adhesive, as a sizing agent for paper, and as a separation agent. The use of chitin as a plant fertilizer is described in U.S. Pat. No. 4,199,496, issued to Peniston et al. As a fertilizer, chitin is added to soil to supply chemical elements (e.g., nitrogen) needed for plant nutrition. Chitin slowly releases nitrogen into the soil thereby increasing the nitrogen content of the soil over a relatively long period of time.
Chitosan has been used as a plant growth regulator, a compound that can inhibit, accelerate, or otherwise influence physiological processes in plants. As described in U.S. Pats. Nos. 4,812,159 and 4,964,894, issued to Freepons, plant growth regulators are substances that are used to influence the growth characteristics of plants and cause some change in the plant""s normal growth pattern. Plant growth regulators influence, for example, germination enhancement, root stimulation, plant stature control, shortening or lengthening of the time to plant maturity, ripening control, increased yield, color control, and shortened or lengthened dormancy.
The Freepons patents describe processes for influencing plant growth by distributing an aqueous solution of deacetylated chitin (i.e., chitosan) in a nonphytotoxic acid (preferably an amino acid) in the soil in which plants are to be grown. These patents note that the chitosan solution can also be applied directly to plant seeds or to the foliage of emerging plants.
Despite the advances in methods for improving agricultural methods, there exists a need for methods and compositions that reduce transpiration and prevent drought-induced wilting of plants. The present invention seeks to fulfill these needs and provides further related advantages.